Microsoft has known about the Dogfood rule for at least twenty years. It's been part of their culture for a whole generation now. You don't eat People Food and give your developers Dog Food. Doing that is simply robbing your long-term platform value for short-term successes. Platforms are all about long-term thinking.
Google+ is a knee-jerk reaction, a study in short-term thinking, predicated on the incorrect notion that Facebook is successful because they built a great product. But that's not why they are successful. Facebook is successful because they built an entire constellation of products by allowing other people to do the work. So Facebook is different for everyone. Some people spend all their time on Mafia Wars. Some spend all their time on Farmville. There are hundreds or maybe thousands of different high-quality time sinks available, so there's something there for everyone.
Our Google+ team took a look at the aftermarket and said: "Gosh, it looks like we need some games. Let's go contract someone to, um, write some games for us." Do you begin to see how incredibly wrong that thinking is now? The problem is that we are trying to predict what people want and deliver it for them.
You can't do that. Not really. Not reliably. There have been precious few people in the world, over the entire history of computing, who have been able to do it reliably. Steve Jobs was one of them. We don't have a Steve Jobs here. I'm sorry, but we don't."
Interesting comment on Google+ as a platform. I love google products. There will be lots of innovation (gmail, google voice, g+ etc) if google provides good APIs to external developers and treat these APIs as first class citizens.